The organ of Corti (Organum spirale cochleae) is the sensory
organ of hearing in man and most animals. Movement of the tympanic
membrane (not visible here) causes auditory bone dislocation. Thus
the foot plate of stapes (the last auditory bone) moves the membrane covering
the oval fenestra which is the entrance to the inner ear. This causes
perilymph movement. The latter is conducted via Membrana vestibuli
to the endolymph in Ductus cochlearis which now moves the Membrana
tectoria. Thereby attached stereovilli
of the sensory inner (1) and outer hair cells (2)
get dislocated which causes impulse change in leaving nerve fibres that
reach the spiral ganglion (VIII). The auditory nerve (Nervus
cochlearis; part of brain nerve VIII)originates here and conducts the
impulses to the brainstem.